Earlier quoted context omitted.
Even modern frontier models benefit so hugely from careful context pruning, maintenance, and rewriting to erase mistakes that it's astonishing to me that there are no tools centered around it. The one tool that used to have such a feature, Zed and its retroactively-named Text Threads, has now stripped itself of it.
this! the back-and-forth chat interface where you can edit only your own messages, and only then to get a new response, is a terrible one, but I think favored by vendors because it helps them fight in vain against prompt injection. Custom harnesses and stuff are nice but incredibly time consuming to set up when all I want to do is like, see what the agent is reading, and editing out some irelevant nonsense side quest…
Afaik messing with the context also pretty reliably degrades performance still. The model responses reference things that no longer exist to it and it becomes more chaotic.
The real usefulness of parallel or sub-agents is not that they run at the same time, its that they isolate noisy or self-contained context away from the main window.